1. Field of the Invention
The present invention relates generally to wireless local area network (WLAN) technology. More particularly, the present invention relates to a increasing data throughput using a block acknowledgement.
2. Description of the Related Art
This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the claims in this application and is not admitted to be prior art by inclusion in this section.
Recently, there has been a great increase in the use of wireless local area networks (WLANs) conforming to the IEEE 802.11 communication standard. WLANs are expected to support the same applications as wired networks that they replace or supplement. The IEEE 802.11e group is developing media access control (MAC) improvements to support quality of service (QoS) sensitive applications, to enable a better mobile user experience, and to make more efficient use of the wireless channel.
FIG. 1 illustrates a prior art communication frame 2 for non-quality of service (QoS) acknowledgements. The communication frame 2 includes a frame control field 3, a duration/ID field 4, a Receiver Address (RA) field 5, and a FCS (frame check sequence) field 6.
The 802.11e specification includes a variety of optional features. One of the optional features is known as block acknowledgements (Block ACK). The legacy 802.11 MAC always sends an ACK frame after each frame that is successfully received. Block ACK allows several data frames to be transmitted before an ACK is returned, which increases the efficiency since every ACK frame has a significant overhead for transmission. Block ACK is initiated through a setup and negotiation process between the Quality of Service station (QSTA) and Quality of Service Access Point (QAP). Once the block ACK has been established, multiple quality of service (QoS) data frames can be transmitted in a contention free burst, with short inter-frame space (SIFS) separation between the frames.
Currently, there are two block ACK mechanisms defined under 802.11e: immediate and delayed. When using immediate block ACK, the sending station transmits multiple data frames in a contention free burst, separated by SIFS. The sender must obey the constraints of the transmit opportunities (TXOP) duration it is currently operating within. At the end of the burst, the sender transmits a block ACK request frame. The receiver must immediately respond with a block ACK frame containing the acknowledgement status for the previous burst of data frames.
The delayed policy allows the group acknowledgement to be sent in a subsequent TXOP following the burst. The same sequence of a contention free burst and block ACK request is used as in the immediate mode. The receiver simply sends a standard ACK in response to the block ACK request, indicating that the block ACK will be delayed. Delayed acknowledgement increases the latency, and is provided to support lower performance implementations that are unable to immediately calculate the ACK.
FIG. 2 illustrates a prior art communication frame for quality of service (QoS) data block acknowledgement. This block acknowledgement is defined in the IEEE 802.11e specification. The block acknowledgement (ACK) structure acknowledges frames within on traffic identifier (TID). The Block ACK acknowledges a block of frames with one signaling message. Nevertheless, the Block ACK is applicable to only one communication traffic stream, identified by a traffic identifier (TID). A traffic stream is a stream of data (e.g., voice and best effort data) associated with a certain traffic specification. The starting sequence control provides a sequence number of the frames starting from the receiver which need to send a block acknowledgement. Every subsequent frame is indicated as a bit in the bitmap. A zero (0) in the bitmap indicates no received and a one (1) in the bitmap means received.
Thus, there is a need to enhance the Block ACK function by aggregating block ACK for different TIDs for a communication station so that it can be applicable to multiple traffic streams. In this way, a communication station with multiple applications can use just one Block ACK instead of requiring a Block ACK for each traffic identifier (TID). Further, there is a need to aggregate multiple frames from different traffic identifiers (TID) to enable the sending of an aggregated block ACK per communication station for multiple TIDs.